JPH104241A - Surface semiconductor optical device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface semiconductor optical device stably operating at low threshold current and high temperature yet having excellent optical characteristics. SOLUTION: This laser diode 10 comprises a first block 12 provided with a first mirror and a second block 14 provided with the second mirror part, an active layer and the third reflecting part, and bonded onto the first block 12. The first block 12 is comprised of the first reflecting part 18 comprising alternately-formed GaAs layers 18a and AlAs layers 18b on a GaAs substrate 16 and a lower part electrode 20. The second block 15 is provided with a second reflecting mirror part 32 made of a third reflecting mirror part 22 of Si/SiO2 layer, an upper part electrode 24, an GaInAsP etching stop layer 26, an InP clad layer 28, a multiquantum well active layer 30, a three layered InP layer 32a and two layered GaInAsP layer 32b interposed between the layers. The first block 12 and the second block are bonded with each other by different- material direct bonding technology. In such a constitution, the bonding interface may be between the second reflecting part 32 and the third reflecting part 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar semiconductor optical device and a method for fabricating the same, and more particularly, to a threshold value so as to be suitably applied in a wide field of optical communication, particularly in an optical interconnection area. The present invention relates to a surface type semiconductor optical device improved to operate stably even at a low temperature and a high temperature, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A surface-emitting type semiconductor laser diode is a surface-type semiconductor optical device having a structure for extracting light in a direction perpendicular to a substrate, and is widely used as an optical transmitter or an optical amplifier in the field of optical fiber communication. Have been. In optical fiber communication, the forward bias current applied to the surface emitting semiconductor laser diode is changed according to the signal, the output is directly modulated, the intensity-modulated light beam is transmitted to the optical fiber, and the light receiving side Detection is performed by a photodiode PD or an avalanche photodiode APD, and a voltage proportional to the intensity of incident light is extracted as a signal.

In order to use a surface emitting semiconductor laser diode in a wider and wider range than the conventional application range, first, a reflection layer sandwiching an active layer of a resonator of the surface emitting semiconductor laser diode should be used. It is necessary to reduce the threshold current by increasing the effective reflectivity of the mirror. Second, the heat dissipation characteristics of the surface type semiconductor optical device are improved, and the device is operated stably at a high operating temperature. It is necessary. For this purpose, studies for improving the effective reflectance and the heat dissipation characteristics have been actively conducted. For example, there is a research example in which the effective reflectivity and heat dissipation characteristics have been improved by introducing a semiconductor multilayer film reflector using a dissimilar material direct bonding technology as a reflector of a vertical cavity surface emitting semiconductor laser diode. It has been reported.

[0004]

However, in the above-mentioned research example, since a multilayer film in which materials having different lattice constants are directly adhered is formed as a reflecting mirror, when the multilayer film is brought close to the active layer, the multilayer film is formed. Lattice defects and strains generated near the bonding interface of the film affect the active layer, and significantly degrade the optical characteristics of the active layer. Therefore, in the above-mentioned research example, the bonding interface is provided at a position sufficiently distant from the active layer. As a result, there is a problem in that the effective reflectance of the reflector decreases due to light absorption in a layer between the active layer and the semiconductor multilayer film reflector. Further, when the area of the light emitting region is made small, there is a problem that the diffraction loss increases and the effective reflectance similarly decreases. In this case, there is a demand that the reflecting mirror composed of a semiconductor multilayer film be brought as close as possible to the active layer, the effective reflectivity should be increased, the threshold current should be reduced, the heat dissipation should be improved, and the upper limit of the operating temperature should be increased. I'm not satisfied. In the above, the conventional technical problem has been described using a surface-emitting type semiconductor laser diode as an example. However, the same applies to other surface-type semiconductor optical devices that emit or emit light perpendicularly to a substrate. .

It is an object of the present invention to provide a surface type semiconductor optical device which operates stably at a low threshold current and a high temperature and has good optical characteristics.

[0006]

In order to achieve the above object, a surface type semiconductor optical device according to the present invention (hereinafter referred to as a first invention) is provided with a surface on which light enters or exits perpendicularly to a substrate. -Type semiconductor optical device, comprising: a first block having a first multilayer semiconductor on a substrate; at least an active layer; and a second multilayer semiconductor provided below the active layer. The second block is formed by directly bonding different kinds of materials onto the first block with the first multilayer semiconductor of the first block and the second multilayer semiconductor of the second block as interfaces. It is characterized by being adhered by technology.

The surface type semiconductor optical device of the present invention comprises a substrate,
Applicable regardless of the type of compound semiconductor. In the first invention, the second multilayer semiconductor is interposed between the active layer and the first multilayer semiconductor, so that the adhesive interface between the first multilayer semiconductor and the second multilayer semiconductor becomes active layer. , The optical characteristics of the active layer can be maintained, and a decrease in the effective reflectance of the resonator can be suppressed by interposing the second multilayer film.

In a preferred embodiment of the first invention, both the first multilayer semiconductor and the second multilayer semiconductor constitute one of the resonators comprising the active layer and a pair of reflectors. Further, a third multilayer semiconductor is provided on the active layer of the second block as the other reflecting mirror of the resonator, and functions as a surface emitting semiconductor laser diode. Further, in a preferred embodiment, both the first multilayer semiconductor and the second multilayer semiconductor have two types of compound semiconductor layers having different refractive indexes n each having an optical thickness of λ / 4n.
, Which is characterized in that it has a laminated structure formed by epitaxial growth alternately.

In the surface type semiconductor optical device according to the first aspect of the present invention, the first block and the second block include a first multi-layer semiconductor surface interposed between the substrate and the active layer, and a second block. Is bonded with the surface of the multilayer semiconductor device as an interface. In another surface-type semiconductor optical device according to the present invention (hereinafter, referred to as a second invention), the first block and the second block are
The surface of the second multilayer semiconductor of the first block having the substrate, the first multilayer semiconductor, the active layer, and the second multilayer semiconductor, and the surface of the third multilayer semiconductor of the second block Bonded as an interface. That is, the surface type semiconductor optical device of the second invention is a surface type semiconductor optical device that makes light enter or exit perpendicular to the substrate, and comprises a first multilayer semiconductor,
A first block having an active layer and a second multilayer semiconductor in sequence on a substrate; and a second block having at least a third multilayer semiconductor. The second block is a first block. Characterized in that the second multi-layered film semiconductor and the third multi-layered film semiconductor of the second block are bonded to each other on the first block by using a different material direct bonding technique.

In the second invention, the second multilayer semiconductor is interposed between the active layer and the third multilayer semiconductor, so that the bonding interface between the second multilayer semiconductor and the third multilayer semiconductor is formed. Is separated from the active layer, the optical characteristics of the active layer can be maintained, and the reduction of the effective reflectance of the resonator can be suppressed by interposing the second multilayer film.

In a preferred embodiment of the second invention, the first multilayer semiconductor, the active layer, the second multilayer semiconductor and the third multilayer semiconductor include a resonator comprising an active layer and a pair of reflecting mirrors. It is characterized by functioning as a surface emitting semiconductor laser diode. Further, a preferred embodiment is a second embodiment.
That each of the multilayer semiconductor and the third multilayer semiconductor has a multilayer structure in which two types of compound semiconductor layers having mutually different refractive indices n are epitaxially grown alternately with an optical thickness of λ / 4n. Features.

The structure of the multilayer semiconductor of the first invention and the second invention is not particularly limited, and two kinds of compound semiconductors having different compositions or different refractive indexes, for example, an AlAs layer and a GaAs layer are alternately laminated. A multi-layered film, or a multi-layered film having an intermediate layer interposed between two types of compound semiconductors having different compositions or different refractive indexes, for example, an A layer between an AlAs layer and a GaAs layer;
A multilayer film having an interposed 1As layer, and a multilayer film having a superlattice layer interposed between two types of compound semiconductors having different compositions or refractive indices, for example, between an AlAs layer and a GaAs layer. A multilayer film having a GaAs / AlAs superlattice layer interposed can be used.

A method for manufacturing a surface type semiconductor optical device according to the present invention is a method for manufacturing a surface type semiconductor optical device for vertically incident or emitting light on a substrate. A first epitaxial growth step of obtaining a first wafer by epitaxial growth on a semiconductor layer;
An active layer and a second multilayer semiconductor formed by epitaxial growth are sequentially formed on another substrate to obtain a second wafer; a second epitaxial growth step of obtaining a second wafer; 2 with the surface of the multilayer semiconductor as an interface,
A step of integrally bonding the first wafer and the second wafer by a dissimilar material direct bonding technique; and a step of bonding the first wafer or the second wafer.
And etching one of the substrates by etching the wafer. The method for epitaxial growth is not particularly limited.
A VD method or the like can be used. The semiconductor layer formed between the active layer and another substrate in the second epitaxial growth step is not particularly limited, and is, for example, a semiconductor layer functioning as an etching stop layer, a multilayer semiconductor functioning as a reflector, or the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments with reference to the accompanying drawings. Embodiment 1 of Surface-Type Semiconductor Optical Device This embodiment is an embodiment in which the surface-type semiconductor optical device according to the first invention is applied to a surface-emitting type semiconductor laser diode, and FIG. It is sectional drawing which shows the lamination structure of a semiconductor laser diode. As shown in FIG. 1, a surface-emitting type semiconductor laser diode 10 of this embodiment (hereinafter simply referred to as a laser diode 10) has a first block 12 having a first reflecting mirror, an active layer, and an active layer. A second reflector provided below the layer; and a second block attached to the first block, comprising a third reflector provided above the active layer. I have.

The first block 12 includes a first reflecting mirror portion 18 formed on a substrate 16 made of GaAs, and a lower electrode 20 provided on a surface of the substrate 16 facing the first reflecting mirror portion 18. It is composed of The first reflecting mirror portion 18 has the same layer thickness λ as the GaAs layer 18a having the layer thickness λ (wavelength) / 4n.
(Wavelength) / 4n AlAs layers 18b are alternately laminated, and the GaAs layer 1 having a thickness of λ (wavelength) / 4n is formed as the uppermost layer.
8a. n is the refractive index of each compound semiconductor layer, and the same applies to the following.

The second block 14 includes, on the side facing the first block 12, a third reflecting mirror portion 22 in which Si layers and SiO ₂ layers are alternately laminated, and an upper surface of the third reflecting mirror portion 22. An upper electrode 24 covered therewith so as to be exposed, an etching stop layer 26 made of GaInAsP, a clad layer 28 made of InP under the upper electrode 24, and a multiple quantum light emitting at a wavelength of 1.3 μm. Well active layer 3
0, and a third reflecting mirror section 32. The third reflecting mirror section 32 has an InP layer (n = 3.2) having a layer thickness of λ (wavelength) / 4n.
1) Ga InA having a layer thickness of λ (wavelength) / 4n as in 32a
sP layer (band gap wavelength 1.2 μm, n = 3.4
2) 32b are alternately laminated, and the lowermost layer has a layer thickness λ.
(Wavelength) / 4n InP layer 32a, that is, three InP layers 32a and two Ga InAsP layers 32 interposed therebetween.
b.

The first block 12 and the second block 14 are composed of a GaAs layer 18a, which is the uppermost layer of the first reflector 18 of the first block 12, and the uppermost layer of the second reflector 32, which is the second block 14. It is bonded to the lower InP layer 32a without using an adhesive by a dissimilar material direct bonding technique using a thermal bonding method.

In the laser diode 10 of this embodiment, since the second reflecting mirror portion 32 epitaxially grown is interposed between the active layer 30 and the contact interface, the first reflecting mirror portion 18 and the second reflecting mirror portion 32 The active layer 30 is not affected by lattice defects and distortion at the bonding interface of
Improves the effective reflectivity of the resonator. In this embodiment, since the effective reflectance is improved, the second reflecting mirror 3
Laser oscillation is possible at a threshold current density of about 1.5 kA / cm ² , which is about half the threshold current density of a conventional surface emitting semiconductor laser diode without 2 and 3 kA / cm ² . .

Modification 1 of Embodiment 1 As shown in FIG. 2A, the first reflecting mirror portion 18 of Embodiment 1 has the same layer thickness λ as the GaAs layer 18a having a layer thickness λ (wavelength) / 4n. (Wavelength) / 4n AlAs layers 18b are alternately stacked. In this modification, the first reflecting mirror portion is a multilayer film having an intermediate AlGaAs layer between the AlAs layer and the GaAs layer, as shown in FIG. 2B, for example. , An AlAs layer 18c, an AlGaAs layer 18d, a GaAs layer 18e, and an AlGaAs layer 18f having a total thickness of λ.
(Wavelength) / 2n. Such a configuration can be similarly applied to the second reflecting mirror unit.

Modified Example 2 of Embodiment 1 In this modified example, the first reflecting mirror section 18 is made of an AlAs layer and Ga.
As a multilayer film having a GaAs / AlAs superlattice layer interposed between the As layer and the GaAs layer, for example, as shown in FIG.
lAs layer 18g, GaAs / AlAs superlattice layer 18h,
GaAs layer 18i and GaAs / AlAs superlattice layer 18
1 is a four-layer structure, so that the entire film thickness is λ (wavelength) / 2n. Such a configuration can be similarly applied to the second reflecting mirror unit.

Embodiment 2 of the Surface-Type Semiconductor Optical Device This embodiment is an embodiment in which the surface-type semiconductor optical device according to the second invention is applied to a surface-emitting type semiconductor laser diode. FIG. It is sectional drawing which shows the lamination structure of a surface-emitting type semiconductor laser diode. As shown in FIG. 3, a surface-emitting type semiconductor laser diode 50 of the present embodiment (hereinafter simply referred to as a laser diode 50) includes a first reflecting mirror section 52, an active layer 54, and a second reflecting mirror section 56, Sequentially, Ga
A first block 60 on a substrate 58 made of As,
It has a third reflecting mirror section 62 and is composed of a second block 64 bonded to the first block. The second block 64 has a top surface of the second reflection mirror portion 56 of the first block 60 and a bottom surface of the third reflection mirror portion 62 of the second block 64 as interfaces, and is made of a different material directly using a thermal bonding method. Due to the bonding technique, they are bonded to each other without using an adhesive.

The first block 60 has a lower electrode 66 on a surface facing the second reflecting mirror section 56. The configuration of each of the first reflector 52, the active layer 54, and the second reflector 56 is the same as the configuration of the first reflector 18, the active layer 30, and the second reflector 32 of the first embodiment, respectively. It is. The second block 64 has an upper electrode 68 on the third reflecting mirror 62. The configuration of each of the third reflecting mirror section 62 and the upper electrode 68 is the same as the configuration of the third reflecting mirror section 22 and the upper electrode 24 of the first embodiment, respectively.

In the laser diode 50 of this embodiment, since the second reflecting mirror portion 56 epitaxially grown is interposed between the active layer 54 and the contact interface, the second reflecting mirror portion 56 and the third reflecting mirror portion 62 The active layer 54 is not affected by lattice defects and distortion at the bonding interface of
Improves the effective reflectivity of the resonator.

[0024] Example embodiment of a method for manufacturing a surface-type semiconductor optical device is an example of applying the present invention a method for making the laser diode 10 of Example 1, 4 and 5, the present embodiment respectively It is sectional drawing which shows the layer structure of the board | substrate for each process of an example method. In order to manufacture the laser diode 10, first, a wafer 40 for forming the first block 12,
A step of forming a wafer 42 for forming the second block 14 is performed.

In the process of forming the wafer 40, as shown in FIG. 4A, a GaAs substrate is formed on a substrate 12 made of GaAs.
The first reflecting mirror portion 18 is formed by epitaxially growing the layers 18a and the AlAs layers 18b alternately, and further, by epitaxially growing the GaAs layer 18a on the uppermost layer. In the step of forming the wafer 42, as shown in FIG.
The etching stop layer 2 is sequentially formed on the substrate 44 made of P.
6, the cladding layer 28 and the multiple quantum well active layer 30 are epitaxially grown, and then the InP layer 32a is formed thereon.
And the Ga InAsP layer 32b are alternately epitaxially grown, and further, the InP layer 32a is epitaxially grown on the uppermost layer to form the second reflecting mirror portion 32.

Next, as shown in FIG. 5A, the wafer 40 and the wafer 42 are heat-treated in a hydrogen atmosphere at a temperature of about 600 ° C. for about 30 minutes, and the first reflecting mirror 1
8 GaAs layer 18a and the second reflector 32 of the wafer 42
The wafer 40 and the wafer 42 are bonded to each other between the uppermost InP layer 32a. Next, as shown in FIG. 5B, the substrate 44 of the wafer 42 is
An etching step of selectively etching up to the above is performed. Thereafter, as shown in FIG. 5C, the etching stopper layer 26, the cladding layer 28, the active layer 30, and the second reflecting mirror 32 are etched into a column shape to form a block having a cross section of a predetermined size. Subsequently, as shown in FIG. 5D, a third reflecting mirror portion 22 composed of a multilayer film of a Si layer and a SiO ₂ film is formed on the etching stopper layer 26, and further, the upper surface of the third reflecting mirror portion 22 is formed. The upper electrode 24 is formed around the third reflecting mirror portion 22 so as to partially expose the first reflecting mirror 22. Together,
The lower electrode 20 is formed on the lower surface of the substrate 12. Through the above steps, the laser diode 10 shown in FIG. 1 can be obtained.

According to the present invention, similar effects can be obtained even in a material other than the above-mentioned material system. For example, AlI having a larger refractive index difference
An nP / GaAs multilayer film reflecting mirror may be configured as the first reflecting mirror section 18, and the gain of the GaI is small with temperature.
An nAs / AlGaInAs system can also be used as a material for the active layer. Further, although the embodiment has been described by taking a 1.3 μm band semiconductor laser diode as an example, this is only an example.
The present invention can be applied to an m-band surface type semiconductor optical device. Further, the present invention is applied not only to the semiconductor laser diode but also to the light emitting diode and the surface type light receiving element, and the second reflecting mirror portion is provided on the surface opposite to the light extraction surface or the light incidence surface, thereby emitting light. It is possible to improve the light emitting efficiency of the diode and the light receiving quantum efficiency of the surface light receiving element.

[0028]

According to the present invention, a multi-layer semiconductor is bonded to a multi-layer semiconductor by a different material bonding technique, and the multi-layer semiconductor is interposed between the bonding interface and the active layer.
Since the influence of lattice defects and strain at the bonding interface does not affect the active layer, a surface semiconductor optical device that operates stably at a low threshold current and a high temperature and has good optical characteristics can be realized. In addition, by applying the method of the present invention, stable operation at low threshold current and high temperature,
Moreover, a planar semiconductor optical device having good optical characteristics can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a layer structure diagram of an embodiment of a surface emitting semiconductor laser diode according to the first invention.

FIGS. 2 (a) to 2 (c) each show a layer structure of a multilayer semiconductor constituting a reflecting mirror section.

FIG. 3 is a layer structure diagram of an embodiment of the surface emitting semiconductor laser diode according to the second invention.

FIGS. 4A and 4B are each a layer structure diagram showing a layer structure of a wafer used for manufacturing the surface emitting semiconductor laser diode shown in FIG.

5 (a) to 5 (d) are cross-sectional views each showing a layer structure in each step when the method of the present invention is performed.

[Explanation of symbols]

Reference Signs List 10 Embodiment 1 of surface type semiconductor laser diode according to the present invention 1 12 First block 14 Second block 16 Substrate 18 First reflecting mirror section 18a GaAs layer 18b AlAs layer 20 Lower electrode 22 Third reflecting mirror section 24 Upper electrode 26 Etching stop layer 28 Cladding layer 30 Multiple quantum well active layer 32 Second reflecting mirror part 32a InP layer 32b Ga InAsP layer 40, 42 Wafer 44 InP substrate 50 Example 2 52 of surface type semiconductor laser diode according to the present invention First reflection Mirror part 54 Active layer 56 Second reflecting mirror part 58 Substrate 60 First block 62 Third reflecting mirror part 64 Second block 66 Lower electrode 68 Upper electrode

Claims (7)

[Claims] 1. A surface-type semiconductor optical device that enters or emits light perpendicularly to a substrate, comprising: a first block having a first multilayer semiconductor on the substrate; at least an active layer; And a second block having a second multilayer semiconductor provided below the second block, wherein the second block comprises a first multilayer semiconductor of the first block and a second multilayer of the second block. A surface type semiconductor optical device, wherein the surface type semiconductor optical device is bonded to the first block with a multilayer semiconductor as an interface by a different material direct bonding technique. 2. The semiconductor device according to claim 1, wherein both the first multilayer semiconductor and the second multilayer semiconductor form one reflector of a resonator including the active layer and a pair of reflectors. 2. The surface type semiconductor optical device according to claim 1, wherein a semiconductor is provided on the active layer of the second block as the other reflecting mirror of the resonator, and functions as a surface emitting semiconductor laser diode. 3. Both the first multilayer semiconductor and the second multilayer semiconductor are obtained by alternately epitaxially growing two types of compound semiconductor layers having mutually different refractive indices n with an optical thickness of λ / 4n. The surface type semiconductor optical device according to claim 2, wherein the surface type semiconductor optical device has a laminated structure. 4. A surface-type semiconductor optical device that enters or emits light perpendicularly to a substrate, comprising: a first multilayer semiconductor, an active layer, and a second multilayer semiconductor on the substrate sequentially. A first block; and a second block having at least a third multilayer semiconductor. The second block includes a second multilayer semiconductor of the first block and a third multilayer film of the second block. A surface type semiconductor optical device, wherein the surface type semiconductor optical device is bonded to a first block by using a different material direct bonding technique with an interface with a semiconductor. 5. A surface-emitting type semiconductor laser comprising: a first multilayer semiconductor, an active layer, a second multilayer semiconductor and a third multilayer semiconductor forming a resonator including an active layer and a pair of reflectors; The surface type semiconductor optical device according to claim 4, which functions as a diode. 6. Both the second multilayer semiconductor and the third multilayer semiconductor are formed by alternately epitaxially growing two types of compound semiconductor layers having mutually different refractive indices n with an optical thickness of λ / 4n. The surface type semiconductor optical device according to claim 5, wherein the surface type semiconductor optical device has a laminated structure. 7. A method for manufacturing a surface type semiconductor optical device for vertically incident or emitting light on a substrate, the method comprising epitaxially growing a first multilayer semiconductor on the substrate to obtain a first wafer. (1) a second epitaxial growth step of sequentially forming a semiconductor layer, an active layer, and a second multilayer semiconductor formed by epitaxial growth on another substrate to obtain a second wafer; A step of integrally bonding the first wafer and the second wafer by a dissimilar material direct bonding technique with the surface of the first multilayer semiconductor and the surface of the second multilayer semiconductor as interfaces; Or a step of etching one of the substrates by etching the second wafer.